When you come to replace heater plate have a look at my post "fisher & paykel DD603 heater plate fuse burnt out." ( not sure how to give link to this post..) includes a comment from someone else as well... I used new seals and they are a bit tight.. but certainly have not leaked!..You will need to follow the manual but it is not that hard.

remember: if running diagnostics.. dont test element without water in the tub.. . it may overheat..